This invention relates generally to the field of fluid infusion devices for medical applications. More specifically, it relates to infusion devices used for the administration of a liquid medicament to a patient from a filled syringe into an intravenous (IV) administration system.
Various devices have been developed for the intravenous (IV) infusion of liquid medicaments into a patient at a controlled flow rate over an extended period of time. For example, gravity flow IV administration sets have been employed for many years, and more recently, IV administration sets with electrically powered pumps have been developed.
There are applications in which a more compact and inexpensive type of infusion device is desired or required. For example, in addition to direct infusion from a syringe, it is frequently necessary to infuse a secondary fluid into a primary IV flow from a gravity flow or electrically-pumped IV administration set. Also, infusion into an ambulatory patient frequently requires an infusion device that is less bulky, less complex, and easier to use than gravity flow or pump-powered devices. For such applications, relatively complex self-powered infusion devices are frequently used.
With a typical, manually actuated IV administration syringe, infusion over an extended period of time is usually impractical or inconvenient, and achieving a substantially constant flow rate throughout the infusion is often difficult. To overcome these problems, the prior art has devised a variety of mechanisms for actuating the syringe so as to achieve a more or less constant fluid flow over an extended period of time. One type of syringe actuation mechanism is that which utilizes either internal or external springs to displace the plunger of the syringe. Examples of such mechanisms are shown in the following U.S. Pat. No.: 4,381,006--Genese; 4,597,754--Thill et al.; 4,608,042--Vanderveen et al.; 4,623,330--Laby et al.; 4,755,172--Baldwin; 4,966,585--Gangemi; 5,078,679--Reese; and 5,100,389--Vaillancourt.
While the spring-powered mechanisms of the prior art over-come, to varying degrees, the above-mentioned problems associated with manual syringes, they suffer from other shortcomings, such as complexity, relatively heavy weight, and relatively high costs. Those with spring mechanisms inside the syringe necessitate increased costs in the manufacture of the syringe itself, making such mechanisms inappropriate for single use, disposable syringes. Those employing a spring mechanism external to the syringe are typically cumbersome to use, often necessitating the extra step of installing the syringe in a dispenser.
Another approach has been to use elastomeric bands to provide the plunger-depressing force in a syringe. Examples of such devices are shown in U.S. Pat. No. 4,636,197--Chu; U.S. Pat. No. 4,950,163--Zimble; U.S. Pat. No. 5,024,662--Menes et al.; and German Democratic Republic (GDR) Patent No. 69,428. The elastomerically powered syringes are typically simpler and less costly to manufacture than the spring actuated devices discussed above. They are also usually easier and more convenient to use, and they are more readily adaptable for single use applications. A principal drawback to these prior art elastomerically powered devices, however, is that they require specially designed syringes, and they are thus not readily adapted for use with standard IV administration syringes.
Therefore, there has been an unfulfilled need for a compact, self-actuated IV administration device that provides a nearly constant flow rate over an extended period of time, while also being economical to manufacture, easy and convenient to use, and adaptable for single use applications with the standard IV administration syringe.